This invention relates generally to syringe devices and particularly to syringe devices that are adapted to shielding a hypodermic needle attached thereto so as to prevent accidental needle contact when the syringe device is not being used.
Health care and other individuals who work in proximity to hypodermic needle type syringe devices are susceptible to accidental and potentially infectious contact with hypodermic needles attached thereto due to careless handling and disposing of the syringe devices after being used.
Several techniques have been proposed in an effort to prevent such accidental needle contacts. In a first technique, advanced in U.S. Pat. Nos. 4,735,618 and 4,139,009, a needle cap or needle assembly component, respectfully, of a syringe device is provided with a shield which collapses upon itself in the syringe direction as the needle end of the shield is pressed against the skin surface (or vial surface) where the injection (or fluid withdrawal) is to be made. A needle assembly component also operating on this principle but for the objective of making the needle hidden at all times from patient view is described in U.S. Pat. No. 3,134,380. However, the technique in these patents not only requires the circumference of the shield to be pressed against the injection surface for the shield to collapse. Thus, if an insufficient area of contact is available or there is an improper alignment of circumference of shield with area of contact then the shield may not properly collapse. But the shield must also stay pressed against the injection surface for the shield to stay collapsed. Thus, during an injection, for example, the needle is at all times, including as it penetrates the patient, completely obstructed from view by the shield, making accurate positioning of the needle against the skin of the patient difficult. In addition, resistance to collapsing of the shield places a positive pressure on the area of tissue surrounding the point of injection (or fluid withdrawal) which can interfere with the injection (or fluid withdrawal) process.
In a second technique, the barrel of a syringe device is provided with a noncollapsible slidable shield which can be manually moved backwardly about the barrel to expose the needle for a use whereafter the shield can be manually positioned forwardly about the barrel to shield the needle after the device has been used. See, for example, U.S. Pat. Nos. 4,898,590; 4,840,619; 4,816,022; 4,801,295; 4,758,231; 4,731,059. However, the shielding mechanism in this technique requires a procedure while the device is being used in this case manually moving the shield to the shielding position after the device has been used. Thus, if the operator forgets to perform this procedure, which can happen during a medical operation, for example, the needle remains unshielded and susceptible to accidental and potentially infectious contact by anyone working in the proximity of the needle.
In a third technique, a needle is retracted into the barrel of a syringe device after being used. See, for example, U.S. Pat. Nos. 4,861,338; 4,838,869; 4,838,863; 4,790,822; 4,747,831; 4,747,830; 4,675,005; 4,026,287. However, this technique too requires a procedure while the device is being used in this case dealing with activation of the retraction mechanism. If the operator forgets to perform this procedure, which can happen during a medical operation, for example, the needle remains exposed and susceptible to accidental and potentially infectious contact by anyone working in the proximity of the needle. There can also be the question of complicated fabrication, increased cost and complicated operation due to requirements of this technique, including that the needle itself be movable and that an actuation mechanism to retract the needle be provided.